[PATCH] Fix ldbl-128ibm ceill, floorl, roundl and truncl zero-sign handling

[Joseph Myers]

On Sun, 18 Jan 2026, Aurelien Jarno wrote:

> When the result of ceill, floorl, roundl and truncl is zero, the sign of
> the result must match the sign of the input. For the IBM 128-bit long
> double format, the sign is determined by the high part.
> 
> Ensure the correct sign when the high part is the result of
> computations, by copying the sign from the input high part to the output
> high part. On POWER, this conveniently maps to the fcpsgn instruction.
> 
> Fixes: BZ #33623

I think there should be tests added (to libm-test-ceil.inc etc.) that test 
these bugs directly rather than relying on testing indirectly via the 
fromfp functions.

-- 
Joseph S. Myers
josmyers@redhat.com